fix: correct type definition of Headers.prototype.values() to indicate it returns an IterableIterator<string> (#740)

Author: harmony7

types/globals.d.ts

@@ -1532,7 +1532,7 @@ interface Headers {
   // Iterable methods
   entries(): IterableIterator<[string, string]>;
   keys(): IterableIterator<string>;
-  values(): IterableIterator<[string]>;
+  values(): IterableIterator<string>;
   [Symbol.iterator](): Iterator<[string, string]>;
 }
 
@@ -1824,4 +1824,4 @@ type KeyFormat =
   | "raw"
   // | "spki";
 type KeyType = "private" | "public" | "secret";
-type KeyUsage = "decrypt" | "deriveBits" | "deriveKey" | "encrypt" | "sign" | "unwrapKey" | "verify" | "wrapKey";
+type KeyUsage = "decrypt" | "deriveBits" | "deriveKey" | "encrypt" | "sign" | "unwrapKey" | "verify" | "wrapKey";